A multidisciplinary approach to regulatory mechanisms that influence the growth, replication, and differentiation of cancer and normal cells is proposed. Studies of DNA and chromatin replication, the transcription and processing of messenger RNA, and the composition and function of nuclear and cytoplasmic membranes are projected. The role of the cell membrane in the control of cell growth and replication will be investigated. Biochemical characterizations of RNA polymerase, DNA polymerase, and other replication-related proteins are projected. Molecular mechanisms involved in the differentiation of Friend leukemia cells, lymphocytes, murine teratocarcinoma cells, and lambda phage will be studied. Plans for introducing genetic methods into the study of cell differentiation in eucaryotic systems are described.